This application claims priority on Japanese Patent Application No. 2001-350,543 filed on Nov. 15, 2001.
1. Field of the Invention
The present invention generally relates to impact power tools. More particularly, the present invention relates to an impact driver which includes a housing containing a motor and further includes a hammer case which is assembled to the front end of the main housing and contains an impact mechanism.
2. Description of the Related Art
An impact driver generally includes a main housing that contains a motor and a hammer case which is assembled to the front end of the main housing and contains an impact mechanism. As disclosed in Japan Published Unexamined Patent Application No. 7-148669, typically, the hammer case and the main housing of such an electric power tool are both provided with protuberances or bosses with screw holes such that the case can be assembled to the housing from the front of the tool by tightening screws into the screw holes.
While this arrangement achieves its intended objective, it is not free from certain problems and inconveniences. For example, the bosses, as they protrude from the outer peripheral surfaces of the main housing and the hammer case, may hinder or interfere with work in tight space, or damage the material, such as a board, being fastened, for example, with screws by the power tool during operation.
In view of the above-identified problems, an important object of the present invention is to provide an impact power tool with a main housing and a hammer case both having a simplified shape so as to improve the ease of use of the tool and work efficiency.
Another object of the present invention is to provide an electric power tool that is free from protrusions that may hinder the use of the tool.
The above objects and other related objects are realized by the invention, which provides an impact tool that includes a main housing containing a motor and having a front end. The tool further includes a hammer case containing an impact mechanism and having a rear end, with the hammer case being assembled to the front end of the main housing. The front end of the main housing includes a first threaded portion, whereas the rear end of the hammer case includes a second threaded portion adapted for threadable engagement with the first threaded portion of the main housing so as to couple the hammer case to the main housing. The impact tool additionally includes a rotation stop mechanism provided in the main housing at a position below the hammer case for engaging an outer surface of the hammer case so as to prevent rotation of the hammer case with respect to the main housing upon coupling of the hammer case to the main housing. Due to the foregoing arrangement (i.e., the threadable engagement between the hammer case and the main housing in combination with the provision of the rotation stop mechanism), the outer surfaces of the main housing and the hammer case are free of obstructive protrusions or protuberances, thus ensuring unimpeded tool operation and greatly reducing the possibility of damaging the material, such as a board, being fastened by the electric tool. The arrangement additionally ensures reliable connection between the main housing and the hammer case. Due to the simplified shapes of the main housing and the hammer case, the manufacture of these components is also advantageously simplified. As there are no protrusions on the hammer case and the internal gear case, there is no need to locate or position the hammer case with respect to the main housing during assembly, thus eliminating at least one step from the entire assembly procedure of the tool.
According to one aspect of the present invention, the hammer case is screwed on the main housing in a first direction so as to couple the hammer case to the main housing. Furthermore, the rotation stop mechanism includes: a plurality of recesses provided in the outer surface of the hammer case; a rack disposed in the main housing for being transversely slidable therein and capable of engaging the recesses; and a screw member which is inserted into the rack from a side surface of the main housing and threadably engages the rack, the screw member being capable of causing the rack to travel in the first direction when tightened into the rack. This arrangement realizes a simply constructed and reliable mechanism for stopping the rotation of the hammer case.
According to another aspect of the present invention, the impact tool further includes an on/off trigger below the hammer case for activating the motor. The rotation stop mechanism is disposed immediately above the on/off trigger between the trigger and the hammer case.
According to still another aspect of the present invention, the main housing includes a forward extending portion protruding therefrom above the on/off trigger and covering a lower portion of the hammer case.
According to yet another aspect of the present invention, the impact tool further includes an illuminant disposed in the main housing forward of the rotation stop mechanism so as to illuminate objects in front of the hammer case. In this way, the illuminant can be disposed in an advantageous position without compromising the simple outer shape of the impact tool.
According to one feature of the present invention, the forward extending portion includes an opening at a front end thereof into which the illuminant is inserted, and furthermore the illuminant is oriented at an upwardly inclined angle.
In one embodiment of the invention, the main housing includes an internal gear case having a ring portion which has an outer peripheral surface. The first threaded portion is provided as an external thread in the outer peripheral surface of the ring portion. Furthermore, the hammer case includes an opening at a rear end thereof The second threaded portion is provided as an internal thread in an inner peripheral surface of the opening of the hammer case.
Other general and more specific objects of the invention will in part be obvious and will in part be evident from the drawings and descriptions which follow.